US3317667A - Error correcting tape telecommunication system - Google Patents

Error correcting tape telecommunication system Download PDF

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Publication number
US3317667A
US3317667A US250577A US25057763A US3317667A US 3317667 A US3317667 A US 3317667A US 250577 A US250577 A US 250577A US 25057763 A US25057763 A US 25057763A US 3317667 A US3317667 A US 3317667A
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Prior art keywords
tape
signals
signal
repetition
transmitted
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US250577A
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English (en)
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Silva Herman Da
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Nederlanden Staat
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Nederlanden Staat
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems

Definitions

  • the invention relates to a telegraph system with error correction by means of repetition cycles of predetermined duration and more particularly such a system provided with a tape transmitter, in which the tape is used as a men'lor Furthermore this invention relates to a system for detecting the presence and location of idle time signals in a repetition cycle, and then only stepping the tape back for those signals in the repetition cycle which have been transmitted from the tape, regardless of how many idle time signals may have been interspersed between, before, and/ or after the signals from the tape.
  • a method involving the switching of the tape transmitter is known from the German patent specification No. 880,314.
  • a difficulty with this method resides in the fact that a repetition cycle is required each time the tape transmitter is switched on and off. This is done in order to ensure the correct impression in the event that a repetition occurs during the switching-on and off. For such systems having a short repetition cycle, e.g. those having three signals in the memory, this means that the tape needs only to be set back three symbols.
  • the tape then must be set back eight signals both when the tape transmitter is swittched off as well as on.
  • the tape when the transmitter is switched on, the tape must at least be placed in the reader at the eighth symbol, so that the tape transport wheel can impart seven backward steps to the tape.
  • This requires both a special adaptation of the message in the tape and a certain degree of attentiveness in laying the tape in the reader. Moreover, every switching-on and switching-off of the transmitter is attended with loss of time caused by this required repetition period.
  • Another object is to substitute for the repetition procedure at the switching-on and switching-off of the tape transmitter, another method to safeguard the correct impression in the case of repetitions during the switching-in and switching-out periods.
  • Another object is to establish a number of forward steps imparted to the tape during the last it rotations (one rotation one multi-element code signal) performed before the start of a repetition cycle in the system, which it signals are stored in the memory.
  • Still another object is to impart to the tape this fixed number of steps in an opposite direction during the inter- 3,317,657 Patented May 2, 1967 val when the BQ signal (i.e., the first signal announcing the repetition in every repetition cycle) is transmitted so that the first symbol to be repeated can be placed right in front of the reading mechanism.
  • the BQ signal i.e., the first signal announcing the repetition in every repetition cycle
  • pausepausepauseAB-CD 1 If, however, the pause signals are transmitted after the tape transmitter has been switched off, the order of transmission of the four signals in the last seven steps will be as follows:
  • A-B-CDpause-pause-pause (2) Another possibility consists in a combination of switchingon and switching-off, the transmitting pattern looking as follows:
  • A-pause-B-p ause-CpauseD (3 In all these three cases it has been established that the number of backward steps amounts to four, but the order of transmission distribution in a repetition cycle is always different. In order that the correct distribution or order of transmission of the trafiic signal in the repetition can be obtained, according to this invention, a shift register has been added to the system. This register stores as many bits as there are signals which must remain stored in the momery for a repetition cycle, which in the given example is seven hits.
  • the number of X-bits in the register indicates the number of steps or signals performed, and in the case of a repetition, a like number of backward steps is then correspondingly imparted to the tape.
  • the number of X-bits in the register indicates the number of transport steps performed and, in the case of a repetition, a like number of backward steps must be imparted to the tape.
  • FIGS. 1 and 2 are schematic time diagrams illustrating the two different sequences of tape reading and signal transmission for systems adaptable to the present invention
  • FIGS. 3 and 4a-4b are schematic time diagrams illustrating various cases which may arise in the application of the invention in the systems of FIGS. 1 and 2, respectively;
  • FIG. 5 is a table illustrating the method employed in the seven cases shown in FIGS. 4a-4b.
  • FIG. 6 is a schematic block wiring diagram of the association of the circuits of this invention with a telegraph terminal circuit.
  • the line XM represents the transmission of the signals at successive transmitter rotations.
  • the line ITR shows when the result of the test for signal transmission (from the tape, for other than a pause signal) indicates an active condition. This active condition depends on whether the tape transmitter has been switched on or not and the indication occurs at defined moments in the transmitter rotation. The moments when ITR can indicate active condition and inactive condition again, are marked by vertical strokes. It is supposed that the tape transmitter is switched on at the moment marked I, at the first short upward arrow at the left.
  • a rotation (a transmitting period) begins, ITR being active, a signal A (in this instance in FIG. 1) is read at the reading-station (line ST) of the tape transmitter and transmitter (line XM), i.e. at the time of the first signal testing moment indicated by the long downwardly pointing vertical arrows between XM and ST.
  • FIGS. 1 and 2 the transport steps or pulses actually occurring are represented by black rectangles, the suppressed steps being represented by white rectangles.
  • the tape transport pulses on line ST may also occur at defined moments in the rotation, notably just before the activating-moments and de-activating-moments or before the indicating moments of ITR.
  • the letter A proves to be transmitted as the first tape signal and the letter F as the last tape signal, the transmitter being supposed to be switched off at the moment marked U, at the last short downward arrow at the right.
  • the letter A lies in the reading-station (see line ST), whereas after the switchingoff the letter G can be found in it. Thus, the first symbol is transmitted and the last is not transmitted.
  • FIG. 3 The four cases of FIG. 3 demonstrate this further.
  • the signal entailing the request for repetition is placed in a circle.
  • the pause transmissions are designated by the symbol for beta ([3), the numbered arrows representing the transport steps.
  • the second system (see FIG. 2) relates to the following:
  • the transmission period immediately following this moment will be used to transmit another pause signal IT or B (line XM), since the first or next transmission period begins just before the ITR indi cates it has become active due to the switching-on.
  • Shift register SR This second system is mostly applied in practice, so that the invention indicates further methods to obtain the correct number of return steps.
  • FIGURES 4a and 4b the figures entailing the request for repetition have been placed in a circle.
  • the pause transmissions are indicated by the symbol for beta (6).
  • the repetition cycle always occurs between the two vertical lines separating eight signal rotations and connected by the bidirectional arrow line and is designated by HC (FIG. 4a at top).
  • the tape transport steps are indicated by an arrow bending to the right and the symbol placed at the right of such an arrow shows what tape signal is in the reading-station after that step.
  • the ITR indication or criterion is active; at moments not marked by arrows, the ITR indication or criterion is inactive.
  • the reference 7x Ret, 5x Ret, etc. placed below each BQ transmission and the arrow bending to the left indicates the necessary number of return steps.
  • the symbol placed at the left of such an arrow indicates which symbol is in the reading-station after the required return steps.
  • SR indicates 7 X-bits (0 Ret) (2) Ret required; SR indicates 4 X-bits (+1 Ret) (3) 1 Ret required; SR indicates 2 X-bits (-1 Ret) (3 over BQ) (4) 3 Ret required; SR indicates 3 X-bits (0 Ret) (5) 6 Ret required; SR indicates 7 X-bits (1 Ret) (,8
  • the shift register element marked 1 contains the bit 0 by the symbol 6, and the ITR indication or criterion is active at the moment when a repetition turns out to be necessary, which is indicated by X in FIG. 5.
  • the 0X condition of the shift register element 1 and the ITR indication serves to shown this.
  • the register is quickly driven around by means of pulses in the BQ transmitting period, and the bit information thus extracted from it is introduced to it again, so that after seven pulses the shift register exhibits the original configuration.
  • Each X-bit extracted entails one forward step of the tape.
  • Another method of determining the number of return steps in a system as mentioned in the second place consists in counting the number of transport steps by means of an additional shift register or counting device.
  • this counting device must have seven stages providing eight criteria, viz 0, 1, 2, 3, 4, 5, 6 and 7.
  • this counter When switched on this counter is put in the O-criterion state and counts every transport step performed.
  • the counter When the counter has reached the final state (state 7), further steps are ignored.
  • Each rotation in which there occurs no transport step causes the counter to record in a backward direction, so to count back.
  • the counter is back in the initial state (state 0), further transport steps not occurring are ignored.
  • the state of this counter at the beginning of a repetition cycle then determines the number of return steps to be performed.
  • FIG. 6 there is shown a block wiring diagram of the circuits which may perform the functions described above in the sections headed Systems I and II and the Shift Register SR.
  • These circuits for a tape transmitting telegraph system comprise primarily the terminal circuits TC which are connected to the two line points P and Q on the conductors to the local repeater.
  • these Tape I traffic signals are read one by one from the tape in the tape transmitter TT and conducted to the terminal circuit TC, which comprises the necessary transmission contacts and relays controlled by the tape transmitter, to give the necessary pulses to the conductor points P and C.
  • a tape stepping means TS Connected to the tape transmitter is a tape stepping means TS which may be stepped forwardly and backwardly under the control of the binary shift register SR corresponding to the number of X-bits which have been recorded in this shift register counter SR for each previous seven signals, if seven is the number in the repetition cycle as for the systems described above.
  • this tape also acts as a memory for the traffic signals which have just been transmitted during the repetition cycle period, and a separate memory circuit for these traflic signals is therefore not required in this system.
  • an idle time beta (,8) signal generator IT which is connected also to the terminal circuits TC for operating the transmitter contacts, and may be controlled by the tape transmitter 'IT as well as the binary shift register counter SR, so that any time the tape transmitter 'IT does not transmit signals, idle time signals (,8) will be generated automatically and transmitted at that station to maintain the synchronism of the circuit from the elements in each signal.
  • the control of these idle time signal [1 by the shift register SR would be under a shift register counter therein which counts the O-bits according to the pattern they were transmitted during the previous repetition cycle of seven signals when a repetition is requested.
  • BQ signal generator BQG to the internal circuits TC, which generator BQG is under the control of the RQ signal or request for repetition signal detector RQD, when a signal is sent back from a remote station that an error has occurred.
  • This BQ signal is generated and transmitted to the remote station as the first signal of each repetition cycle, to indicate to the remote station that the signals which follow in the repetition cycle are being repeated, and that those which have already been correctly received should be ignored.
  • a signal receiver OS connected to the terminal circuit TC from which the properly and correctly received signals may be laced on a Tape II.
  • the error detector ED Connected to the signal receiver is the error detector ED. Errors may be detected easily in multi-element signals if these signals are converted into a multi-element balanced code and the elements are then counted to see if they are in the proper balance.
  • the error detector circuit ED associated with each signal receiver OS, tests the balanced code of each received signal, before it is converted into the code for placing on the Tape II.
  • the error detector circuit ED operates the RQ signal generator circuit RQG which generates a special signal for transmission back to the remote sending station, such as by applying a higher or different potential to one of the points P and/ or Q from the terminal circuit TC, to indicate to the remote station that repetition is required.
  • the error detector circuit ED blocks the Tape II for the repetition cycle number of signals.
  • an RQ signal is received at a station, it is not printed on the Tape II by the signal receiver OS, but it controls the RQ signal detector RQD which in turn operates the binary shift register counter SR to start the repetition cycle at that station also and at the same time ope-rates the BQ signal generator BQG for sending back the first signal of the repetition cycle to indicate at the remote station that the request for repetition has been received correctly.
  • this BQ signal when received is blocked from the tape as occurring during the repetition cycle at its receiving station.
  • the traffic signals from the Tape I are transmitted interspersed with idle time signals 8 in a specific pattern, that these signals be retransmitted in this pattern, under the control of the binary shift register SR, particularly for propagation times shorter than the length of time for completing the repetition cycle.
  • idle time signals 6 and message or traflic signals alternately occur throughout a repetition cycle, or if the message signals occur at the first part of the repetition cycle followed by idle time signals and their pat- :terns are not maintained on repetition or retransmission, :an overlap may cancel out one or more of these signals, or there might be a repetition of unwarranted signals.
  • (A) means (TS) for stepping said tape forwardly and backwardly so that it can act as a memory for said traffic signals
  • (B) means (TT) for transmitting said trafiic signals (A, B, C,) from said tape,
  • (C) means (IT) for transmitting idle time signals ([3) when said traflic signals are not being transmitted from said tape, and
  • SR shift register means
  • said shift register means comprises a binary counter for separately counting traffic (X) and idle time signals (0) and recording the pattern in which they were sent during the previous said number of signals in said repetition cycle.
  • said shift register includes a counting means for counting one more than the number of signals in said repetition cycle, which said counting means adds the number of traffic signals sequentially transmitted up to the number of signals in the repetition cycle and stops, and diminishes by the number of idle time signals up to the number of signals in the repetition cycle and then stops.
  • a telecommunication system for multi-element code signals between two stations comprising:
  • a tape means (TAPE 1) recording traffic signals at one station,
  • (E) means (TS) for stepping said tape means forwardly and backwardly whereby said tape means also acts as a memory for said traffic signals
  • (E) means (OS) at another station for receiving said signals
  • (H) means (RQG) at said other station for transmitting a request for repetition signal (RQ) to said one station when an erroneous signal has been detected by said detecting means,
  • (I) means (ED, OS) at said other station for starting a blocking cycle of it signals to block the recording of the next 11 signal received, when an erroneous signal has been detected
  • (J) means (RDQ) at said one station for receiving said request for repetition signal (RQ),
  • (K) means (BQR) responsive to the receipt of said request for repetition signal to start a repetition cycle of it signals and transmit as the first signal of said cycle an answer-back signal (BQ) that said repetition is following, and
  • a system according to claim 8 wherein said shift register also controls the retransmitting of said traific sig- NEIL C. READ, Primary Examiner. nals and idle time signals in said repetition cycle in the same sequential pattern as they were originally trans- 10 ROBINSON Asslslmt Exammer' mitted.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Communication Control (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)
US250577A 1962-01-18 1963-01-10 Error correcting tape telecommunication system Expired - Lifetime US3317667A (en)

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NL273728A NL123421C (xx) 1962-01-18 1962-01-18

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US (1) US3317667A (xx)
JP (1) JPS4812641B1 (xx)
BE (1) BE627212A (xx)
CH (1) CH417675A (xx)
DE (1) DE1167878B (xx)
GB (1) GB983613A (xx)
NL (1) NL123421C (xx)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3483510A (en) * 1965-03-26 1969-12-09 Ericsson Telefon Ab L M Error detecting and control device in a data transmission system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3460090A (en) * 1964-11-06 1969-08-05 Ericsson Telefon Ab L M Apparatus for error correction in a data transmission system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2944248A (en) * 1955-02-23 1960-07-05 Curtiss Wright Corp Data transfer device
US2965124A (en) * 1957-11-04 1960-12-20 Seaside Oil Company Twin angle valve
US3038961A (en) * 1959-06-29 1962-06-12 Western Union Telegraph Co System for detecting errors in telegraph transmission

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL98117C (xx) * 1955-07-26

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2944248A (en) * 1955-02-23 1960-07-05 Curtiss Wright Corp Data transfer device
US2965124A (en) * 1957-11-04 1960-12-20 Seaside Oil Company Twin angle valve
US3038961A (en) * 1959-06-29 1962-06-12 Western Union Telegraph Co System for detecting errors in telegraph transmission

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3483510A (en) * 1965-03-26 1969-12-09 Ericsson Telefon Ab L M Error detecting and control device in a data transmission system

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NL273728A (xx) 1964-09-10
BE627212A (xx) 1963-05-16
DE1167878B (de) 1964-04-16
JPS4812641B1 (xx) 1973-04-21
CH417675A (de) 1966-07-31
GB983613A (en) 1965-02-17
NL123421C (xx) 1968-01-15

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